This invention relates to blood pressure measurements, and more particularly to a blood pressure cuff that may be easily installed around the arm and released.
Hypertension in adults is regarded as a significant health risk since the symptoms of the disease are not apparent to the individual. The presence of the disease in the individual may therefore remain hidden until a catastrophic health event, such as a heart attack, or a stroke occurs. Fortunately, initial diagnosis of the condition is easily accomplished by a simple blood pressure measurement. Consequently, automatic blood pressure monitoring stations have become widely available to the general public that allow blood pressure measurements to be self-administered. An example of one such system is the VITA-STAT(trademark) blood pressure monitoring station manufactured by Spacelabs Medical, Inc. of Redmond, Washington, which is shown in U.S. Pat. No. D-371,844 to Sadritabrizi, et al. Briefly, the VITA-STAT(trademark) station consists of a kiosk, in which a test subject can be accommodated in a sitting position. The test subject then places an upper arm into a blood pressure cuff apparatus that constricts the flow of blood in an artery to obtain blood pressure measurements at systole and diastole. A processor accepts and processes blood pressure signals obtained from the cuff apparatus during the examination, and subsequently displays the processed information to the test subject on a monitoring device.
A significant difficulty encountered in self-administered blood pressure measurements is the application of the blood pressure cuff to the test subject. The flat, flexible cuff commonly associated with the sphygmomanometer is particularly unsuited for use in automatic blood pressure monitoring stations, since the application of the flexible cuff around the arm of the test subject is difficult to accomplish without assistance. Moreover, once properly positioned, it must be secured into place by hooks, elastic bands, or specialized fasteners such as VELCRO(trademark). As a consequence, a number of automatic cuff devices have been developed for use with automatic blood pressure monitoring stations. An example of a self-installing cuff apparatus is described in U.S. Pat. No. 4,109,646 to Keller, which uses a motor-driven rotating drum to continuously wrap a blood pressure band onto a limb of a test subject that is placed within the drum. Removal of the blood pressure band from the test subject is accomplished by reversing the motor. A similar technique is described in U.S. Pat. No. 4,206,765 to Huber, which uses a motor driven tensioning drum to tension the blood pressure band around the limb of a test subject. A slip clutch is provided to prevent over tensioning of the blood pressure band during the application of the band to the test subject. U.S. Pat. No. 3,935,984 to Lichowsky, et al., uses a mechanical cable wrapped around the blood pressure band to snug the band tightly about the arm of the test subject. Release of the test subject""s arm is similarly accomplished by reversing the direction of the motor.
A significant shortcoming of these prior art devices is that they rely on a blood pressure band tensioning means that requires a blood pressure band tensioning drive motor and mechanism, which adds to the cost and complexity of the blood pressure monitoring station. Further, since the tensioning means is motor driven, some means must be provided to allow the test subject to release the blood pressure cuff in the event of a power failure, or to protect the test subject from over-tensioning the band due to system malfunctions. The release mechanisms employed in prior art devices have not, in general, adequately addressed these abnormal operating conditions. Additionally, a particular shortcoming present in the prior art devices is that there is no provision for a release mechanism that allows the band tension and the pneumatic pressure in the band to be released simultaneously through a user actuated release.
The self-installing cuff used with the VITA-STAT(trademark) blood pressure monitoring station mentioned previously does not rely on a motor driven tensioning means to snug the blood pressure band about the arm. Instead, the arm is tightly confined within a fixedly mounted cylindrical housing that retains the inflatable blood pressure band. The use of a cylindrical, non-resilient member to retain the inflatable band also has some drawbacks. A limit on the maximum cylinder diameter exists because the blood pressure band must achieve adequate snugness prior to inflation. Since the cylinder diameter is generally sized according to median estimates of upper arm diameter, some individuals may find that the cylindrical cuff apparatus simply cannot accommodate them. In other cases, some individuals may damage the flexible blood pressure band inside the cylinder by unsuccessfully attempting to insert their upper arms into the cylinder, which may render the blood pressure cuff apparatus unusable, or cause it to yield inaccurate measurements. Still other individuals may misalign the upper arm with the cylindrical housing so that a successful inflation of the blood pressure band is impeded, resulting in an erroneous blood pressure reading. Finally, some individuals may find the insertion of the arm into a closed cylindrical member that subjects the arm to a constriction too psychologically intimidating to use.
A further drawback present in all prior art cuff devices is that they lack an ergonomic adjustment feature. Typically, automatic blood pressure devices, such as the VITA-STAT(trademark) blood pressure monitoring station, accommodate the test subject in a seated position while undergoing a blood pressure test. Since the orientation of the cuff assembly cannot be adjusted, the test subject must make suitable adjustments in body position to properly align the arm in the cuff assembly prior to inflation of the internal band, and maintain the arm in the aligned position until the blood pressure evaluation is complete. As a consequence, individuals whose bodily dimensions significantly differ from median estimates cannot be accommodated by the blood pressure cuff in a comfortable manner.
Accordingly, there is a need in the art for a cuff assembly that does not use a motor driven band tensioning devices to tension the band prior to inflation, and that provides a cuff release capability to a greater degree than present in prior art devices. Further, there is also a need in the art for a cuff apparatus that does not rely on a confining cylindrical member to retain the inflatable band. Finally, the cuff assembly should provide an ergonomic adjustment capability that will permit the proper alignment of the blood pressure cuff with the arm to be conveniently attained during a blood pressure measurement, which, at the same time, enhances the comfort of the test subject.
Other advantages of the invention will become apparent based upon the description of the invention provided below when read with reference to the drawing figures.
The present invention is directed to a method and apparatus for obtaining blood pressure measurements employing a user releasable and adjustable blood pressure cuff. In one aspect of the invention, the blood pressure cuff apparatus consists of a first cuff member connected to a mounting surface and rotatable about a first axis of rotation substantially perpendicular to the mounting surface. The first cuff member is connected to a second cuff member that is rotatable about a second axis of rotation that is substantially perpendicular to the first. A blood pressure cuff comprised of a loop adapted to receive the arm of a test subject is connected to the second cuff member. In another aspect of the invention, the elongated flexible band has a first end and a second end. The first end is connected to the second member of the cuff housing, and the second end is connected to a cuff retainer. The cuff retainer is releasibly latchable from the second member so that the elongated flexible band forms a loop to snugly fit the arm of the test subject with a first circumferential length when the cuff retainer is latched. When the cuff retainer is unlatched, the elongated flexible band forms a loop with a second circumferential length, which allows the arm of the test subject to be easily withdrawn.